Conventionally, it has been suggested that receiving millimetric wave radiated from an object such as human body to image the object and detecting a metallic or non-metallic weapon or smuggled goods hidden in the object from the captured image (for example, Patent Documents 1 and 2).
In this type of millimetric wave imaging device, a planar antenna in which a plurality of antenna elements are arranged in a two-dimensional form is used as an antenna for receiving millimetric wave and an object image using the millimetric wave is formed on a surface of the planar antenna through a lens antenna, so that the object image is received from each antenna element of the planar antenna.    Patent Document 1: Japanese Unexamined Patent Publication No. 09-197042    Patent Document 2: Japanese Unexamined Patent Publication No. 2003-177175